从字符串值中获取某些子字符串

Question

I have the following dates:

"Friday, January 31",
"Wednesday, February 12",
"Monday, February 17",
"Wednesday, March 5",

I want to set up a string function where I am given the number always:

31
12
17
5

I started with this function:

String strCheck = suspendedDates[i];
int pos = strCheck.length();
int pos2 = strCheck.indexOf(" ");

I am stuck right now, because how does it know which " " is it?

Can someone help me with the function.

Answer 1

use lastIndexOf() instead of indexOf()

final String str = "Friday, January 31";
System.out.println(str.substring(str.lastIndexOf(" ")));

• Ideone demo

Answer 2

Get the substring from the end. Instead of trying to figure out locations

strCheck.substring(strCheck.length()-2);

This will take the last two characters. Then just do a trim() in case it's a single character to remove the space:-

strCheck.substring(strCheck.length()-2).trim();

Alternative

The other option as mentioned is to do a lastIndexOf() on the String with a space (" ") as an argument which will search backward from the end of the String till it finds the space. But as the number can always be extracted in 2 character spaces, I see no reason to do 2 character compares every time you want to extract a known size String (2) in a known location ( length()-2 ) in order to retrieve the location that you already know.

Answer 3

作为@JigarJoshi答案的替代方法，如果您不介意，可以使用正则表达式，删除所有非数字字符。

String result = dateString.replaceAll("[^\\d]+","");

Answer 4

I had to post it; since this is a date I would go with Date parse to allow an additional check on the format of the inputs:

An alternative way:

SimpleDateFormat format = new SimpleDateFormat("EEEE, MMMM DD");
Calendar cal = Calendar.getInstance();

cal.setTime(format.parse("Friday, January 31"));
System.out.println(new SimpleDateFormat("DD").format(cal.getTime()));

2nd SimpleDateFormat("DD") is used instead of deprecated getDate() .

Answer 5

If you are trying to divide the string into parts for parsing, i suggest using String.split(" "), look at the javadocs and the internet for lots of nice examples of this in use! :)

Answer 6

You can use something like this:

 String str = "Friday, January 31";
 Scanner s = new Scanner(s);
 s.useDelimiter( "\\D+" );
 while ( s.hasNextInt() ){
   s.nextInt(); // get int
 }